This invention relates to ignition systems suitable for internal combustion engines and more particularly to a highly reliable ignition system in which optically generated signals selectively trigger individual capacitive discharge ignition circuits for each combustion chamber in the engine.
Ignition systems for modern internal combustion engines often employ capacitive discharge circuits. In such circuits, a storage capacitor is periodically charged from a D.C. voltage source and then a gated electronic switch such as a triac or a silicon controlled rectifier (SCR) is triggered into conduction to discharge the capacitor through the primary winding of an ignition coil. The resulting high voltage output from the ignition coil is applied through a distributor to a preselected spark plug for initiating ignition within an engine cylinder. Originally, capacitive discharge ignition systems were triggered by a conventional set of cam operated breaker points. More recently, the breaker points sometimes have been replaced with other types of trigger signal sources, such as inductive pick-ups, magnetic pick-ups and optical sensors.
Although prior art ignition systems have been satisfactory for many applications, such as in automotive engines, they have not been altogether satisfactory for industrial applications for various reasons. Many industrial internal combustion engines are operated in environments which require a high degree of reliability and an explosion-proof construction. For example, reliability is of the utmost importance in an internal combustion engine used for driving a pump installed in a crude oil pipeline in cold environments such as in Alaska. If the pump is stopped for more than a few minutes, the crude oil will solidify and block the pipeline due to the cold temperatures. On the other hand, in an engine operated on an off-shore oil platform in the Gulf of Mexico, the ignition system must be of an explosion-proof construction to prevent the ignition system from accidentally starting a fire or causing a catastrophic explosion which would not only destroy the expensive platform and related equipment, but would also endanger the lives of many people working on the off-shore platform. Exposed arcing at conventional breaker points and distributors, for example, can easily cause a fire or an explosion when an engine is operated in an explosive environment.